age_str = input('please input your age.')
age = int(age_str)
if age > 17:
    print('ok')
else:
    print('too young')

isQuite = False
while not isQuite:
    age_str = input('please input your age.')
    if age_str == 'quit':
        isQuite = True
        continue
    age = int(age_str)
    if age > 17:
        print('ok')
    else:
        print('too young')
